I know this was addressed to Bill, but I was going to post some new
anthropology information today about this subject. Most anthropologists
dont believe that erectus had fur. The details are covered in my web page
article
http://www.isource.net/~grmorton/sweat.htm
and on page 88-95 of Adam,Apes and Anthropology
The short reason for this belief is that the large brain of erectus (which
utilizes a huge percentage of the metabolic energy) requires an efficient
cooling mechanism. Sweating is believed to have evolved to help maintain a
constant body temperature. Fur would get in the way of the effective
cooling prodigious sweating provides. Mankind sweats like no other animal
being able to move 24 liters of water through the sweat glands in a 12 hour
period. The Evaporation from the skin is essential to maximize the cooling
effect. evaporation from fur, is less efficient. Walker and Shipman write:
"The antiquity of this bodily adaptation to heat stress told us something
else too: the boy was probably running around in hot, open country and
sweating. Although it is indirect evidence, the boy's body build suggests
that he, and all Homo erectuses, had lost whatever body fur or hair our
more ancient ancestors probably possessed. If he had been hairy or furry,
then panting (and avoiding activity during the hottest hours of the day)
would have served as his main mechanism for heat loss, as it does for the
other animals of the Africa savanna." ~ Alan Walker and Pat Shipman, The
Wisdom of the Bones, (New York: Alfred Knopf, 1996), p. 196
The hairlessness would require clothing in colder climates. Also, the need
for an efficient cooling mechanism which is required by a large brain is
in turn related to pain in childbirth. And what is interesting to me is
that the large brain is created by a unique human pattern of brain growth.
All other primates except man double their brain size from birth to adult
hood. The fetal brain growth rate for other primates is rapid, but it slows
dramatically at birth. But their offspring are born able to communicate and
to walk and run as other members of their speices. But this is not the case
in humans. The fetal brain growth rate continues for the first year of
life, at which time, the baby begins to communicate verbally and begins to
attempt its species specific locomotion pattern. Measured by brain growth
rate, onset of communicative abilities and locomotion, we should expect
human gestation to be 21 months, not 9 months.
H. erectus shared with us this uniquely human pattern of birth. But what I
learned this morning was that H. rudolfensis, the earliest member of our
genus (dated to 2.4 million years from Malawi) also shared this uniquely
human birth and brain development pattern. They tripled their brainsize
from birth to adulthood rather than having the apelike doubling pattern.
Since their brain sizes were not that much smaller than erectus brains,
this would imply that
sweating, hairlessness and the human birth pattern was in existence as
early as 2.4 million years. See Steven M. Stanley, Children of the Ice
Age, (New York: Freeman 1998), p. 163-165
I would also point out that H. rudolfensis stood 5 foot 8 inches tall,
about the average height of modern Americans, yet they weighed only about
130 pounds. this skinny body shape would be similar to that Walker and
Shipman found in erectus and would imply a response to the heat load they
and the erectus' experienced on the savanna.
One final note, apparently the existence of fur and a large brain are
incompatible. Chimpanzees are forest creatures not savanna creatures. If
they were to inhabit the savannas as our ancestors did, they would need to
change their hair.
"A second ecological parameter that may be limiting to chimps making a run
onto the savanna is heat load. As everyone knows, chimps have black hair
all over their bodies. A black surface absorbs heat from incident
sunlight, rather than reflecting it. Thus the amount of heat absorbed by a
black-haired chimp on a cloudless day in the savanna is much greater than
the amount of heat absorbed by the same chimp in the shade of the forest,
even if the ambient air temperature is the same. The chimp's heavy coat of
hair also insulates its body from lsing heat by convection with the
surrounding air currents. A chimp therefore must avoid getting overheated
or run the risk of dying from heat prostration. In the forest the chimp's
hair functions to keep it warm when it is cold, especially at night,
relativeely dry when it is raining, and to protect its skin frm insects and
from minor injur. The hotness and dryness of the savanna, the type of
habitat in which people tend to do well, may then actually be the effective
barrier to chimp dispersal out of the forest." ~ Noel Boaz, Eco Homo, (New
York: Basic Books, 1997), p. 122
Other authorities on hair:
"How might these features be interpreted in a functional and evolutionary
way? There is the remarkable thermo-regulatory function of eccrine sweat
glands. Sweating can deliver two litres of water to the skin surface in
two hours and carry off almost 600 calories of heat. Hair tends to trap
moisture, so that sweat evaporation is more effective with reduced hair.
Interestingly, the number of hair follicles in humans is similar to that in
chimpanzees and gorillas, but the much reduced size of hair shafts in
humans gives a hairless appearance." ~ Adrienne L. Zihlman and B. A. Cohn,
"Responses of Hominid Skin to the Savanna," South African Journal of
Science, 82:2, (1986), p. 307-308, p. 308
"As a direct consequence of a naked skin man has the most effective body
cooling system of any living mammal." ~ P. E. Wheeler, Dept. of Biology,
Liverpool Polytechnic, "The Evolution of Bipedality and Loss of Functional
Body Hair in Hominids," Journal of Human Evolution, (1984), 13:91-98, p. 91
glenn
Adam, Apes and Anthropology
Foundation, Fall and Flood
& lots of creation/evolution information
http://www.isource.net/~grmorton/dmd.htm